Thermal relay



Dec. 13, 1938. R. T. KINTZING THERMAL RELAY Filed Sept. 12, 1934 INVENTOR Reese T/zfzrzzzz'ng.

ATTOINEY WITNESS Patented Dec. 13, 1938 UNITED STATES PATENT OFFICE Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of,

Pennsylvania Application September 12, 1934, Serial No. 743,635

11 Claims.

My invention relates to protective devices and particularly to thermal relays.

An object of my invention is to provide a relatively simple, compact and easily manufactured and assembled thermal relay comprising a minimum number of parts.

Another object of my invention is to provide a thermal relay that shall operate substantially instantaneously in response to abnormally heavy in or excessive overloads'in the circuit and with a predetermined time delay in response to long continued moderate overloads in the circuit.

Another object of my invention is to provide I a thermal relay comprising easily interchangeable parts to adapt it to circuits of different normal current values.

Another object of my invention is to provide a thermal relay comprising easily adjusted means for varying the current value at which the relay will operate.

A still further object of my invention is to provide a thermal relay comprising a bimetal latch that shall be conductively heated by a secondary coil carried by the latch and traversed by an alternating-current flux to inductively heat the coil.

A still further object of my invention is to provide a thermal relay of the type using a saturated magnetizable core having a relatively large amount of leakage flux which is utilized to energize the movable armature and contact member.

Still another object of my invention is to provide a thermal relay that, shall be serviceable from the front of the switchboard or panelboard on which it is mounted argi in which a relatively simple operation on the part ofan operator will reset the relay after operation thereof because of excess current in the circuit controlled thereby.

Other objects of my invention will either be .10 pointed out hereinafter or will be apparent from the following description of one form of device embodying my invention now preferred by me.

In practicing my invention, I provide a closedcircuit magnetizable core having a primary cur- 45 rent-traversed winding on one part thereof and a.

the magnetizable core, and is held in its actuated.

position by a resilient latching or holding means. Both parts of the armature move under long continued moderate overload conditions in the circuit when the bimetal latch has moved to release the entire armature structure.

In the accompanying singlesheet of drawings:

Figure 1 is a top plan view of a device embodying my invention, shown as being mounted on a base plate,

Fig. 2 is a view in front elevation thereof, removed from the base plate,

Fig; 3 is a view in side elevation, of the parts shown in Fig. 1, showing the relay in its normal position,

Fig. 4 is a view in vertical section therethrough taken on the line IV-IV of Fig. 3, removed from the base plate,

Fig. 5 is a detail view of the lower part of the relay showing the operated position of the armature after an abnormally heavy overload in the circuit, and r Fig. 6 is a view similarto Fig. 5 but showing the operated position of the armature as the result of a long continued moderate overload in the circuit.

I have illustrated a thermal relay II as mounted on a panelboard or switchboard I3 of the usual kind made of electric-insulating material. The relay assembly includes more particularly a. single frame plate 15 for supporting all but one of the other elements of the relay, this frame plate being of substantially L-shape in section and made of non-magnetic material. One portion I! of the frame plate is bent at substantially right angles to the main part thereof and is secured against the panelboard [3 by a plurality of short machine screws IS in a manner well known in the art.

A two-part transformer core includes a front portion 2| and a rear portion 23, each built up of a plurality of magnetic sheets or laminations of substantially L-shape, as will be seen particularly from the side view of Fig. 3 of the drawing. A suitable number of such thin magnetic sheets are secured together as by hollow rivets or by some other means well .known in the art to provide the self-contained portions 2| and 23, it being noted that these two portions are identical and are merely reversed in position to provide a substantially closed magnetic circuit having at least one 7 air gap 25 therein which is provided for a specific purpose to'be hereinafter referred to in detail. It is, of course, obvious that a second air gap 21 will be present but no particular use is made of this in the operation of the relay.

of short machine screws II.

The two portions 2| and 23 are secured against the inner surface of frame plate I in front of the flange portion I! by a plurality of short machine screws 29, two such screws being provided for each of the portions 2| and 23, these machine screws or bolts being located adjacent to the respective end portions of the sets of laminations. Non-magnetic spacers 3|, of tubular shape, are provided between the one surface of the sets 2| and 23 and the frame plate I5 to properly space the magnetic core from its supporting plate.

A primary winding comprising a coil 33, wound on a spool'35 of electric-insulating material is located on the longer leg of the front portion 2| of the magnetic core and, while no terminals are shown for this coil, it is to be understood that such are provided by me and that they may be located on the panelboard I3 or in any other desirable location. The winding 33 is, of course, designed with reference to the constants of the magnetic circuit and also with reference to the normal current traversing the circuit which is to be protected by the thermal relay I I, and I may here point out that it is my intention to provide a number of different coils having different sizes of conductors therein, in order to adapt the relay for use in circuits of different normal current-carrying capacity.

A plural-part movable armature structure is pivotaly mounted on and suported by a second flange portion 31 of frame plate I5 and includes a lower or outer bar or tongue portion 39 which is substantially flat except for a bowed-out portion 4| having an opening 43 therethrough, the convex surface of portion 4| being adapted to rest on the upper surface of flange 31 and be held thereon by a pin 45 extending through the opening 43 and fixed in flange 31. A second pin 4'1 is located in front of pin 45 and is also secured to flange 3'! as by riveting thereto. The pin 41 extends upwardly the same as pin 45 and the outer tongue portion 39 is provided with a recess 49 at its front end through which the pin 47 extends to maintain the bar 39 in the desired alignment with the magnetic core and a small distance therebelow.

The armature structure includes also an inner or upper magnetic bar or tongue 5| supp d by the front end of bar 39, a bowed-out portion 53 being provided in member 5| to permit of easy tilting movement of member 5| on the forward end of member 39. A spring 55 surrounds pin 41, and a washer 51 and stop pin 59 operate to bias the plural-part armature structure to the position shown in Fig. 6 of the drawing. Tongue 5| is provided with an opening 6| therethrough through which extends pin 45, so that both the outer and the inner bars of the plural-part armature structure are maintained in parallel and substantially coextensive alignment with each other.

A contact member 63 is secured to bar 5| adjacent the inner end thereof and extends through an opening 65 in the outer tongue 39. Contact member 63 is adapted to engage a resiliently mounted cooperating contact member 91 which is shown as being of substantially channel shape in lateral section and as being supported by a small metal bracket 89 secured against the front surface of panel-board i3 by a plurality The bracket 99 is provided with a pin I3 rigid therewith extending through contact member 61, a helical spring 15 surrounding the pin I3 and being held thereon by a washer TI in order-to yieldingly press the forward end of contact member 61 upwardly and into engagement with contact members 93 when the plural-part armature is in the position shown particularly in Fig. 3 of the drawing.

A thermally actuable latch is provided in the form of a bimetal strip I9 located in front of the front surface of panelboard I3 and having its upper end fixedly mounted against the front surface of flange II, a heat-insulating plate 8| being interposed between the strip I9 and flange IT in order to reduce the flow of heat from the bimetal strip to its supporting member. A pair of short machine screws 83 extend through the strip I9, the plate 8| and into flange IT. The bimetal strip is so located that under normal conditions its lower end is located above armature tongue 39 and in engagement therewith substantially as shown in Fig. 3 of the drawing and will, when heated, move toward the panel-board to release the armature in a manner to be hereinafter described in detail.

Means for heating the latch includes a closedcircuit secondary winding 85 which I preferably make either of copper or of aluminum, the object being to obtain as much heat in the closedcircuit secondary winding by the inductive effect of the flux traversing the magnetic core generated by winding 33, as is possible. The coil 85 may be in the form of a small sheet or plate having a suitable opening 81 therein and a flange portion 89 at its rear end by means of which it is secured to the front surface of bimetal latch 19 as by rivets 9| in order that it may have a good engagement with the bimetal latch to conduct heat thereto and to move therewith.

Under certain conditions of operation of the relay, inner tongue member 5| may move alone toward the magnetic core to the position shown in Fig. 5 of the drawing and, in order to hold the tongue member 5| in such actuated position, I provide the front end of the main leg 39 or horizontal portion thereof with an opening 93 through which there extends a resilient bar 95 which may be of L-shape having a bump 91 therein. The tongue portion 5| is further pro, vided with a front and upwardly-extending portion 99 to provide means for resetting the armature structure by an operator. The normal position of portion 95 in the opening 93 is shown in Fig. 3 of the drawing, and the relative positions of these two parts when tongue member 5'I has been actuated is shown in Fig. 5 of the drawing, from which it will be noticed that the outwardly biased end portion 95 holds the tongue member 5| in its actuated position. The resilient latch 95 is secured to the flange portion 31.

I provide also easily operable manually actuable means for varying the current value at which the relay will operate, this means including a magnetizable bar IIlI which is secured against the inner face of the main part of frame the core, this spacer extending between th! side of magnetic core (as seen in n if the drawing) and the righthand or outer surface of bar IOI. At the upper end of bar EM. I provide an adjustable bolt I91, of magnetic material, extending through the frame'plate I5 and the bar I 0|, the inner end of the body of the bolt being normally spaced a. small distance from the upper end of the magnetic core portion 23, substantially as shown in Fig. 4 of the drawing. Means for holding the bolt I01 in any selected adjusted position is provided in the form of a resilient latch I09 made of a barof spring metal having a return bent flange portion as shown in Figs. 2 and 4 of the drawing which latch is secured by the short machine screws I03 against frame plate IS.

The operation of the device embodying my invention may briefly be set forth as follows: The winding 33 is connected in circuit with an electric energy translating device of any kind, such as a motor, transformer or other appliance traversed. by an electric current and subject to overloads. It is to be further understood that a suitable circuit interrupter or switch is provided having either a holding coil or an interrupting coil which is to be controlled by the relay II and more particularly to be controlled by the cooperation of contact members 63 and 61 hereinbefore described.

As long as the value of the current traversing the circuit to be protected is normal, the value of the current traversing coil 33, which may be either connected directly in the circuit or in a derived circuit, in a manner well known in the art, will be relatively small and the amount of current flowing in the short-circuited secondary winding 85 will also be small. Let it be assumed for illustrative purposes that an excessively heavy overload occurs such as may be caused by a locked rotor in a motor or a short-circuit, such overload current traversing, either directly or proportionally, the winding 33. The value of the flux traversing the magnetic circuit of the closed-circuit core hereinbefore described, will not have a linear relation to the value of the current traversing the winding 33 which, as has already been stated, may be the same as that traversing the circuit or may be proportional thereto. The magnetic leakage of the core will be relatively high, this being a natural result of the design employed, not only because of the shape of the core as shown more particularly in Fig. 3 of the drawing, but also because of the use of at least one air gap, namely that identified by numeral 25. In case of such excessive overload current, the leakage flux leaving the magnetic core and traversing at least the inner tongue member 5| of the armature will be so great that this part of the armature structure will be moved upwardly substantially instantaneously to the position shown in Fig. 5 of the drawing, whereby disengagement of the cooperating contact members 53 and 61 is effected. In this way the control circuit in which these two contact members are connected is interrupted to thereby efiect substantially instantaneous interruption of the circuit to be controlled by thermal relay II. The inner tongue member 5| will be held in this actuated position until the operator makes an inspection of the relay and resets the same as by pushing inwardly on the end portion 99 to return the tongue member 5| to its original position.

Let it now be assumed that the circuit con trolled by the relay is traversed by a long continued average overload, which if continued for a sufficient length of time would cause damage to the energy-translating device connected in the circuit. In this case the short-circuited current in secondary coil 85 will be sufliciently large .to cause a temperature rise in the coil ,85

which is communicated to bimetal latch I9 and will cause the same, particularly its lower end, to move toward panel-board I 3 and ultimately out of engagement with the rear end oftongue 39. Consequently, the rear portion of both parts of the armature structure will be moved upwardly by the action of spring 55 into the positions shown in Fig. 6 of the drawing, whereby the control circuit is interrupted by disengagement of contact members 63 and 61. Here again, it is only necessary for the operator to push inwardly on the upper end of portion 99 to reset the device assuming, of course, that he permitted a suflicient length oftime to elapse to permit cooling of the latch 19 and its return to its original position, substantially that shown in Fig. 3 of the drawing, so that it will again be operative to hold the armature structure in the desired position shown in Fig. 3 of the drawing where contact members 63 and 61 are in engagement. It is, of course, obvious that if the operator attempts to return the armature structure to its original position before bimetal latch 19 has cooled sufficiently, the armature will not be held in the position shown in Fig. 3 of the drawing, thus making it necessary to permit some time to elapse so that the lower end of latch 19 will be in engagement with the upper surface of the rear end of tongue portion 39 even though it may not have moved to the position shown in Fig. 3 of the drawing, but will be located nearer to the rear end of tongue 39. The relay embodying my invention thus distinguishes between exceedingly heavy momentary overloads and between long continued overloads, the same result being obtained, namely that of interrupting the circuit, but this result being obtained with different operations, particularly of the two parts of the plural-part armature.

The hereinbefore-described means for varying the value of the circuit current at which the device will operate may be easily and quickly adjusted, as by turning the bolt I01, and it is obvious that the nearer the inner end of the body of the bolt is to the magnetic core, the greater will be the amount of flux shunted out of the closed-circuit secondary coil 85, and therefore, the greater will be the value of the circuit current necessary to cause the relay to operate, this, of course, applying particularly to the moderate overloads and practically not at all to the momentary overloads. It will be noted that actuation of the relay is caused by the effect of useful and of leakage flux in the case of moderate overloads and by the use of leakage flux alone in the case of excessively heavy overloads.

If it is desired to adapt the relay for use on a different circuit, one in which the normal current is quite different from that previously obtaining, it is only necessary for an operator to remove the two securing bolts 29 in the front portion 2| of the core and then remove this portion and the coil 33, and then replace these parts by other parts in which the coil 33 has a different currentcarrying capacity. This makes it very easy to adapt the relay to circuits of different normal current-carrying capacities. This Work of exchange or replacement can be done from the front of the panelboard and it is to be noted that resetting of the device is also effected from thefront of the board.

While I have illustrated and described a parare to be placed thereon as are imposed by the prior art or are set forth in the appended claims.

I claim as my invention:

1. In a thermal relay, the combination with a magnetizable core, a primary winding thereon and a structure including a movable armature controlled by the core, of a bimetal latch normally holding said structure in a predetermined position, and a closed-circuit secondary winding located in operative relation to the core, supported by the bimetal latch and movable therewith.

2. In a thermal relay, the combination with a magnetizable core, a primary winding thereon and a structure including -a movable armature controlled by the core, of a bimetal latch normally holding said structure in a predetermined position, a closed-circuit secondary winding located in operative relation to the core, supported by the bimetal latch and movable therewith, and a single member for supporting the core, said structure and the bimetal latch. v

3. In a thermal relay, the combination with a magnetizable core, a current-traversed primary winding on the core, a structure including a movable armature and means biasing said structure to a certain position, of a bimetal latch normally holding said structure in another position, and a closed-circuit secondary winding supported by the bimetal latch in operative relation to the magnetizable core and adapted to heat the bimetal latch by direct heat conduction thereto.

4. In a relay for protecting an electric circuit from long-continued moderate overloads and from heavy overloads, a movable structure biased to one position and including an armature, a temperature-responsive latch operatively engaging said structure normally holding it in a second position, and means energized responsively to the current in the circuit to be protected for heating the temperature-responsive latch, said means including an inductively heated closed loop directly supported by the latch to heat the same by conduction.

5. In a relay for protecting electric circuits, in combination, a magnetizable core having a closed magnetic circuit, a current-traversed coil on the core, a movable structure biased to one position and including an armature, a bimetal latch normally holding said structure in another position, a closed-circuit secondary coil sur rounding the core and directly supported by th bimetal latch and adapted to heat the latch to eifect movement of said structure when the primary coil has been traversed by a current of a predetermined value for a certain length of time, and adjustable magnetizable means paralleling that part of the magnetic circuit of the core surrounded by the secondary coil to vary the value of the relay current at which said structure is moved.

6. A device as set forth in claim 4 and including magnetic means for varying the inductive heating effect in the closed loop to thereby vary the value of the long-continued moderate overdoad at which movement of said structure occurs.

7. In a thermal relay for protecting an electric circuit, in combination, a frame plate, a magnetizable core secured to the frame plate, a current-traversed energizing coil on the core, a twopart movable structure supported by the frame plate adjacent to the magnetizable core, the outer part of said structure being pivotally supported by the frame plate. the inner part of said structure constituting an armature and being pivotally supported by the outer part and having a contact member extending through the outer part and a cooperating contact member below said structure.

8. In a thermal relay for protecting an electric circuit, in combination, a frame plate, a. magnetizable core secured to the frame plate, 9. ourrent-traversed energizing coil on the core, a twopart movable structure supported by the frame plate adjacent to the magnetizable core, one part of said structure constituting an armature and being pivotally mounted on and movable relatively to the second part and means carried by the frame plate to hold said armature in its final position.

9. In a thermal relay for protecting an electric circuit, in combination, a frame plate, a magnetizable core secured to the frame plate, a current-traversed primary coil on the core, a bimetal strip supported at one end on the frame plate, heat-insulating means between the bimetal strip and the frame plate, a closed circuit secondary coil surrounding the core and secured to the bimetal strip, a plural-part structure pivotally supported on the frame plate adjacent to the core, resilient means biasing said structure to one position, the outer part thereof being normally engaged by the bimetal strip to hold both parts in a second position, the inner part of said structure constituting an armature and being movable independently of the outer part, and resilient means carried by the frame plate for holding the armature in its actuated position.

, 10. In a thermal relay for protecting an electric circuit, in combination, a magnetizable core, a two-part movable structure located adjacent to the core and biased to one position and including 40 an armature, a thermally-actuable bimetal latch to hold said structure in a second position, and means integral with one of said parts of.the movable structure to effect return of said structure to said second position after movement to said one position by manual actuation thereof from the front of the relay.

11. A relay for controlling a circuit. subjected to long-continued moderate overload currents and to excessive overload currents and comprising a magnetizable core, means for variably magnetizing said core in accordance with the overload currents in the circuit, and a movable structure including a normally open armature controlled by the core, a flat closed-circuit secondary coil on one portion of said core, a bimetal strip extending at substantially right angles to said armature in its closed position and in mechanical and thermal engagement with said secondary coil, said bimetallic strip controlling a latching connection with a portion of said movable structure, said armature being actuable with a time delay by the combined effects of said windings and the v resultant unlatching of said connection by said bimetallic strip being heated by said secondary coil for moderate overload currents and said armature being actuable relatively quickly by the effect of said first-named winding alone for excessive overload currents;

REESE T. KINTZING. 

